Method and device for producing workpieces with a non-circular internal and/or external shape

ABSTRACT

In a method for producing workpieces having inner and/or outer contours deviating from a circular shape, at least one workpiece is clamped on a machine and the workpiece is driven in rotation about a rotational axis of the workpiece at a first constant velocity. At least one tool is arranged on a carriage that is moveable radially to the rotational axis of the workpiece as well as axially in the longitudinal direction of the rotational axis of the workpiece. The tool is rotatably driven about a rotational axis of the tool that deviates from the rotational axis of the workpiece such that an active cutting surface of the tool moves on a circular path at a second constant velocity. The second constant velocity is selected such that its revolutions per minute deviate from the revolutions per minute of the first constant velocity with respect to size and/or rotational direction.

BACKGROUND OF THE INVENTION

The invention relates to a method for producing inner and/or outercontours deviating from a circular shape on a machine with clamping ofat least one workpiece that is rotatably driven at a constant speed andof at least one tool, especially for machining by cutting, wherein thetool is moveable by a carriage radially to the rotational axis of theworkpiece as well as axially in the longitudinal direction of thisrotational axis. Furthermore, the invention relates to a device forperforming this method.

A method for producing workpieces with polygonal outer and/or innercontours by a cutting machining process is known from European patent 0097 346. In this known method, the workpiece guided on a circular pathengages during the entire revolution at a workpiece whereby the pathvelocity of the tool is respectively changed during each revolutionaccording to a periodic movement law. This permanent change of the pathvelocity of the tool during each revolution requires, in addition toprogrammable functional transmitters for the tool drive, a transmissionthat is controlled according to Pascal curves. Accordingly, this knownmethod allows the manufacture of a plurality of polygonal outer andinner contours. However, because of the permanent control of the pathvelocity of the tool it requires a great control-technological andmachine-related expenditure so that this method can be performed only ondevices that are specially designed for this method and havecontrollable transmissions for the tool drive.

It is an object of the invention to provide a method for producing innerand/or outer contours deviating from a circular shape with which innerand/or outer contours deviating from a circular shape can be produced asdesired with minimal control-technological expenditure and withcommercially available devices. Furthermore, the invention has theobject to provide a device for preforming this method.

SUMMARY OF THE INVENTION

The solution of this object in regard to the method is inventivelycharacterized by the tool with its effective surface being rotatablydriven about a tool axis on a circular path with constant velocity thatdeviates from the revolutions per minute of the workpiece with respectto size and/or direction of rotation, whereby the tool axis is differentfrom the rotational axis of the workpiece.

Due to the different velocities and optionally different rotationaldirections of the constantly rotating workpiece, on the one hand, aswell as due to the different rotational centers and the selectableradius of the circular movement path of the effective tool surface, aplurality of contours of movement paths of the effective tool surfaceresulting from the afore-mentioned parameters are produced. The specialadvantage of this method is that, despite the constant rotationalvelocities of the workpiece and of the tool, different contoursdeviating from the circular shape can be produced and that, on the otherhand, this method can be performed on conventional devices because fordriving the tool mounted on a carriage only a separate drive but nocomplicated controllable transmission for coupling the rotary velocitiesbetween tool and workpiece is necessary. The contour of the contour thatdeviates from the circular geometry is thus only dependent on therespective constant ratio of the revolutions per minute of the axes ofrotation, the radius of the outer circle described by the tool as wellas the axial offset of the axes of rotation.

According to a preferred embodiment of the inventive method thedifference of the revolutions per minute between the workpiece, on theone hand, and the tool, on the other hand, is an integer. Therevolutions per minute differences in integers will result, for example,for a ratio of 2:1 in triangular and for a ratio of 3:1 in quadrangularcontours.

In an alternative embodiment of the inventive method the plurality ofcontours to be produced can be further increased such that the tool axisitself is driven on a circular path with constant velocity that deviateswith regard to size and/or rotational direction from the revolutions perminute of the tool about an eccentric axis which deviates from the toolaxis.

The three possible axes of rotation, i.e., the tool axis, the workpieceaxis, as well as the eccentric axis, extend parallel to one anotheraccording to one embodiment of the invention. The parallel extendingaxes of rotation result in a straight inner and/or outer contour of theworkpiece, i.e., a contour parallel to the axis of the workpiece.

According to a further embodiment of the invention, the position of therotational axes relative to one another can be individually adjusted. Byadjusting the position of the axes of rotation, the so-called phaseangle, screw-shaped outer and/or inner counters can be produced.

For changing the diameter of the contour deviating from the circulargeometry as well as for producing conical and spherical contours it issuggested, in a further development of the invention, that the radius ofthe outer circle described by the tool can be continuously adjusted by across-slide rest rotating with the axis of rotation of the tool andarranged on the tool spindle.

The solution to the object with regard to the device is characterized inthat the tool, on the one hand, is clamped on a tool spindle and isrotatably driven on a circular path with constant velocity that deviatesfrom the revolutions per minute of the workpiece with regard to sizeand/or rotational direction about a tool axis which is different fromthe rotational axis of the workpiece.

Finally, it is suggested with the invention that the tool axis isarranged eccentric to the tool spindle and is driven on a circular pathwith constant velocity, that deviates from the revolutions per minute ofthe tool with regard to size and/or direction of rotation, about aneccentric axis which is different from the tool axis. This additionalaxis of rotation allows the manufacture of a plurality of new innerand/or outer counters deviating from the circular shape. Especially, themanufacture of individual depressions within the workpiece wall or evenpenetrations of the workpiece wall can be provided with this inventivedesign of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention result from thefollowing description of the attached drawing in which three embodimentsof an inventive device are represented. The drawing shows in:

FIG. 1a a schematic design of a first embodiment without eccentric axis;

FIG. 1b a schematic design of a further embodiment without eccentricaxis, however, comprising a cross-slide rest;

FIG. 2 a schematic design of a device with eccentric axis;

FIG. 3 a triangular polygon contour producible with a device accordingto FIG. 1;

FIG. 4a a quadrangular polygon figure with straight sides produciblewith a device according to FIG. 1;

FIG. 4b a polygon contour with concave sides corresponding to FIG. 4a;

FIG. 5a FIG. 5a a pentagonal polygon contour with concave sidesproducible with a device according to FIG. 1;

FIG. 5b a polygon contour with straight sides corresponding to FIG. 5a;

FIG. 6 a polygon figure produced with a device according to FIG. 2;

FIG. 7 a polygon contour produced with a device according to FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the drawings FIGS. 1a, 1 b, and 2 the principal design of twoembodiments of a device for performing the method for producing innerand/or outer contours deviating from a circular shape is schematicallyshown. A machine not represented in detail, for clamping at least oneworkpiece, has a workpiece spindle 1 with which the workpiece isrotatably driven about rotational axis 2 of the workpiece. The devicecomprises furthermore a carriage 3 by which a workpiece spindle 4 ismoveable radially to the rotational axis 2 of the workpiece as well asaxially in the longitudinal direction of the rotational axis 2 of theworkpiece.

According to FIG. 1a the tool 5 is arranged at the tool spindle 4 whichis rotatably driven on a circular path with constant velocity, deviatingfrom the revolutions per minute of the workpiece, about a rotationalaxis 6 of the tool. In the drawing the spacing between the axis ofrotation 2 of the workpiece and the axis of rotation 6 of the tool isidentified by reference letter x. The spacing between the active surfaceof the tool 5 and the axis of rotation 6 of the tool is indicated byreference letter w.

The embodiment represented in FIG. 1b has a cross-slide rest 9 arrangedon the tool spindle 4 in a fixed manner by which, upon movement of thetool 5 in the direction of the double arrow, the circular radius of thetool 5 is determined.

The second embodiment shown in FIG. 2 of a device for preforming themethod for producing inner and/or outer contours deviating from acircular shape has a tool 5 rotating not only about the rotational axis6 of the tool but also about an eccentric axis of rotation 7 that isradially displaced relative to axis 6. The spacing between the axis ofrotation 6 and the eccentric axis of rotations 7 is indicated aseccentricity e. The revolutions per minute of the rotatably drivencomponents rotating about the rotational axes 2, 6, and 7 is alwaysconstant but different with respect to size and/or rotational direction.In, the embodiments represented in the drawings FIGS. 1 and 2 therotational axes 2 and 6, respectively, 2, 6 and 7 are arranged parallelto one another. However, a spacial offset arrangement of the rotationalaxes 2 and 6, respectively, 2, 6, and 7 to one another by apredetermined angle is also possible.

The representations 3 through 7 described in the following show in anexemplary fashion inner and/or outer contours which are producible withdevices according to drawings FIGS. 1 and/or 2.

FIG. 3 shows a workpiece 8 having a triangular polygon contour. As therepresented point of attack of the tool 5, shown as an example, at thetool 8 shows, this polygon contour can be produced as an outer and/orinner contour. The parameters named in the following for producing sucha triangular polygon contour show that they can be produced with adevice according to FIG. 1, i.e., without eccentricity e. Based on theinteger ratio of −2 to 1 of the revolutions per minute, the representedtriangular polygon contour results. The minus sign of the revolutionsper minute about the rotational workpiece axis 2 shows that therotational direction is counter to the rotation about the rotationalaxis 6 of the tool. In the drawing FIG. 3 the spacing between the axisof rotation 2 of the workpiece and the axis of rotation 6 of the tool isindicated, corresponding to FIG. 1, with x and the one between theactive surface of the tool and the axis 6 of the tool with w. In thetable they are indicated as radii.

workpiece eccentric tool radius 2.0 0.0 18.0 phase angle 0.0 0.0 0.0revolutions −2.0 0.0 1.0 per minute

In FIG. 4a a workpiece 8 with a quadrangular polygon contour is shown.As can be seen from the correlated parameter table, this polygoncontour, deviating from that of FIG. 3, has been achieved simply bychanging the ratio of the number of revolutions from −2:1 to −3:1.

workpiece eccentric tool radius 2.0 0.0 18.0 phase angle 0.0 0.0 0.0revolutions −3.0 0.0 1.0 per minute

FIG. 4b shows a quadrangular polygon contour but with concavelyextending sides. As can be taken from the corresponding parameter table,this change of the profile of the sides of the polygon contour has beenachieved by changing the spacings x and w.

workpiece eccentric tool radius 5.0 0.0 15.1 phase angle 0.0 0.0 0.0revolutions −3.0 0.0 1.0 per minute

FIG. 5a shows a workpiece 8 with a pentagon-shaped polygon contour. Ascan be seen in the parameter table, this polygon contour has beenachieved by changing the ratio of the number of revolutions to a ratioof −4:1. All other parameters correspond to those of the contoursaccording to FIG. 3 and FIG. 4a.

workpiece eccentric tool radius 2.0 0.0 18.0 phase angle 0.0 0.0 0.0revolutions −4.0 0.0 1.0 per minute

FIG. 5b shows also a pentagon-shaped polygon contour but this pentagonhas straight sides in comparison to the pentagon shown in FIG. 5a. Thechange of the profile of the sides of the pentagon has been achievedagain by changing the parameters of the spacings x and w as can be seenfrom the corresponding parameter table.

workpiece eccentric tool radius 1.3 0.0 18.7 phase angle 0.0 0.0 0.0revolutions −4.0 0.0 1.0 per minute

FIG. 6 is a workpiece 8 with a polygon contour that has been producedwith the aid of the device according to FIG. 2, i.e., with an additionaleccentric axis of rotation 7. As can be seen in the drawing as well asin the corresponding parameter table, the spacing indicated by x betweenthe axis of rotation 2 of the workpiece and the axis 6 of the toolcorresponds to the eccentricity e.

workpiece eccentric tool radius 2.0 2.0 18.0 phase angle 0.0 0.0 0.0revolutions −2.0 3.0 1.0 per minute

FIG. 7 shows a workpiece 8 that has a triangular, helical and conicallyextending polygon contour. As can be taken from the correspondingparameter table, the helical extension as well as the conical embodimentof the workpiece contour has been achieved in that during movementaxially in the longitudinal direction of the axis of rotation 2 of theworkpiece for every cut preformed by the tool 5 the phase angle of theaxis of rotation 2 of the workpiece to the axis of rotation 6 of thetool as well as the spacing x have been changed. The helical contour isproduced by the changing phase angle. The conical embodiment of theworkpiece 8 is achieved by the uniform change of the spacing x betweenthe axis of rotation 2 of the workpiece and the axis of rotation 6 ofthe tool along the axis of rotation 2 of the workpiece.

workpiece eccentric tool 1. First cut radius 14.0 3.0 11.0 phase angle40.0 0.0 0.0 revolutions 1.0 −2.0 1.0 per minute 2. Second cut radius13.0 3.0 11.0 phase angle 40.0 0.0 0.0 revolutions 1.0 −2.0 1.0 perminute 3. Third cut radius 12.0 3.0 11.0 phase angle 20.0 0.0 0.0revolutions 1.0 −2.0 1.0 per minute 4. Fourth cut radius 11.0 3.0 11.0phase angle 10.0 0.0 0.0 revolutions 1.0 2.0 1.0 per minute 5. Fifth cutradius 10.0 3.0 11.0 phase angle 0.0 0.0 0.0 revolutions 1.0 −2.0 1.0per minute

As can be seen from the above examples, according to drawings FIGS. 3-7,different inner and/or outer contours deviating from the circular shapecan be achieved by changing only one of the fixedly programmableparameters. These parameters, once set, especially the revolutions perminute, remain constant during the entire machining process. Only forproducing helical and/or conical contours an adjustment of individualparameters during advancement of the carriage 3 along the axis ofrotation 2 of the workpiece is necessary. The different velocities andoptionally rotational directions of the constantly rotating workpiece 8,on the one hand, and the tool 5, on the other hand, as well as thedeviating rotational centers and the selectable radii of the circularmovement paths will result in the multiple contours based on theaforementioned parameter-generated movement path of the active surfaceof the tool which, despite constant rotational velocities, results indifferent profilings. When, for example, the spacing x between theworkpiece axis of rotation 2 and the axis of rotation 6 of the tool isgreater than the radius w of the movement path of the tool 5, a polygoninner contour will result, for example, as a function of the rotationaldirection and the differential revolutions per minute while the reverseratio results in a corresponding outer contour.

As can be seen from the above description, with the disclosed method,respectively, the corresponding device different inner and/or outercontours deviating from a circular shape can be produced withconventional machines.

The specification incorporates by reference the entire disclosure ofGerman priority document 196 24 722.5 of Jun. 21, 1996 as well as ofInternational Application PCT/EP97/03274 of Jun. 23, 1997.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

List of Reference Numerals

1 Workpiece spindle

2 Axis of rotation of workpiece

3 Carriage

4 Tool spindle

5 Tool

6 Axis of rotation of tool

7 Eccentric axis of rotation

8 Workpiece

9 Cross-slide rest

x Spacing between rotational axes of workpiece and tool

w Spacing between active surface of tool and rotational axis of tool

e Eccentricity

What is claimed is:
 1. A method for producing workpieces having innerand outer contours deviating from a circular shape, said methodcomprising the steps of: clamping at least one workpiece on a machineand driving said workpiece in rotation about a first rotational axis ofsaid workpiece at a first constant velocity; arranging at least one toolon a carriage so as to be moveable radially to said first rotationalaxis of said workpiece as well as axially in the longitudinal directionof said first rotational axis of said workpiece; rotatably driving saidtool about a second rotational axis of said tool that deviates from saidfirst rotational axis of said workpiece such that an active cuttingsurface of said tool moves on a circular path at a second constantvelocity; selecting said second constant velocity such that therevolutions per minute deviate from the revolutions per minute of saidfirst constant velocity, wherein the deviation of said second constantvelocity of said tool from said first constant velocity of saidworkpiece is a deviation of at least one of the sizes of said first andsecond constant velocities relative to one another and the directions ofsaid first and second constant velocities relative to one another.
 2. Amethod according to claim 1, wherein in said step of selecting thedifference between the revolutions per minute of said first constantvelocity and of said second constant velocity is an integer.
 3. A methodaccording to claim 1, further including the step of driving said of saidtool on a circular path about a third eccentric axis deviating from saidsecond axis of rotation of said tool at a third constant velocity whilealso rotating said tool about said second axis of rotation, wherein therevolutions per minute of said third constant velocity deviate from therevolutions per minute of said second constant velocity with regard tosize and rotational direction.
 4. A method according to claim 1, whereinsaid first, second, and third rotational axes of said tool and of saidworkpiece extend parallel to one another.
 5. A method according to claim1, further comprising the step of individually adjusting a position ofsaid first, second, and third rotational axes of said tool and of saidworkpiece to one another.
 6. A method according to claim 1, wherein aradius of an outer circle described by said tool is continuouslyadjustable by a cross-slide rest rotating with said tool about saidsecond rotational axis of said tool.
 7. A device for performing themethod according to claim 1, said device comprising: a workpiece spindle(1) having clamped thereto at least one workpiece (8) and driving saidworkpiece (8) at a first constant velocity; at least one tool (5)clamped on a tool spindle (4); a carriage (3) on which said toot spindle(4) and said tool (5) are arranged; said tool (5) moveable by saidcarriage (3) radially relative to a first rotational axis (2) of saidworkpiece (8) as well as axially in the longitudinal direction of saidrotational axis (2) of said workpiece (1); wherein said tool (5) isrotatably driven by said tool spindle (4) about a second rotational axis(6) of said tool (5), which deviates from said rotational axis (2) ofsaid workpiece (1), on a circular path at a second constant velocitythat deviates from the revolutions per minute of said first constantvelocity, wherein the deviation of said second constant velocity of saidtool (5) from said first constant velocity of said workpiece (8) is adeviation of at least one of the sizes of said first and second constantvelocities relative to one another and the directions of said first andsecond constant velocities relative to one another.
 8. A deviceaccording to claim 7, wherein said second rotational axis (6) of saidtool (5) is arranged eccentrically to said tool spindle (4) and saidtool is driven on a circular path at a third constant velocity about athird eccentric axis (7) that deviates from said second rotational axis(6) of said tool (5) while also rotating said tool about said secondrotational axis (6), wherein said third constant velocity deviates fromthe revolutions per minute of said second constant velocity with respectto size and rotational direction.
 9. A device according to claim 7,further comprising a cross-slide rest (9) arranged fixedly on said toolspindle (4) in order to continuously adjust a radius of an outer circledescribed by said tool (5).